A mysterious stomach bug that's made more than 285 people sick has now spread to Illinois. And as this outbreak expands, health experts are still trying to figure out the source.

Doctors say it's not likely going to kill you, but it will make you feel awful for several weeks. It is a nasty bacteria that's causing the illness.

Cyclospora is a parasite that is occasionally found in human stool.

Scientists suspect the parasite travelled by water that came in contact with the stool to the food chain.

Scientists have yet to pinpoint the source of the bacteria that is causing this outbreak, but they're pretty sure it's in some variety of fresh imported produce.

In the past cyclospora has been discovered attached to snow peas, berries and basil- always food imported from outside the U.S.

"It's what we call a food-borne outbreak. They'll find that produce and they'll remove that from the shelves, and it should quiet down," said Dr. Lamar Hasbrouck, Illinois Department of Health.

In the meantime, the outbreak has spread to eleven states but so far includes just one case in Illinois, in the Springfield area.

And that patient recently spent time in Iowa, which along with Texas, is considered the epicenter of this outbreak.

But it usually takes about a week after exposure to the bacteria before patients exhibit symptoms. Doctors say those symptoms include stomach pain and diarrhea. Sometimes there is weight loss, bloating, and fatigue. Without treatment it can last as long as a month.

"Some of these illnesses that are transmitted via food, or vegetables and fruit, can be devastating," said Dr. Max Brito, UIC Infectious Diseases.

Dr. Brito says the key is diagnosing it, because the treatment is fairly simple.

"It is treatable, it's actually treatable with a very simple, very cheap antiobiotic," said Dr. Brito.

Doctors suspect there are many more cases that have not been diagnosed.

But they also say at this point there is not much danger of an epidemic in Illinois, because it appears whatever produce is causing it is not available in this state. You can protect yourself by thoroughly washing or boiling any fresh produce before eating it.